Superconductivity in Ca-intercalated bilayer graphene: C2CaC2.

The deposition and intercalation of metal atoms can induce superconductivity in monolayer and bilayer graphenes. For example, it has been experimentally proved that Li-deposited graphene is a superconductor with critical temperature Tc of 5.9 K, Ca-intercalated bilayer graphene C6CaC6 and K-intercalated epitaxial bilayer graphene C8KC8 are superconductors with Tc of 2-4 K and 3.6 K, respectively. However, the Tc of them are relatively low. To obtain higher Tc in graphene-based superconductors, here we predict a new Ca-intercalated bilayer graphene C2CaC2, which shows higher Ca concentration than the C6CaC6. It is proved to be thermodynamically and dynamically stable. The electronic structure, electron-phonon coupling (EPC) and superconductivity of C2CaC2 are investigated based on first-principles calculations. The EPC of C2CaC2 mainly comes from the coupling between the electrons of C-pz orbital and the high- and low-frequency vibration modes of C atoms. The calculated EPC constant λ of C2CaC2 is 0.75, and the superconducting Tc is 18.9 K, which is much higher than other metal-intercalated bilayer graphenes. By further applying -4% biaxial compressive strain to C2CaC2, the Tc can be boosted to 26.6 K. Thus, the predicted C2CaC2 provides a new platform for realizing superconductivity with the highest Tc in bilayer graphenes.

Superconductivity of monolayer functionalized biphenylene with Dirac cones.

Monolayer biphenylene is a new two-dimensional (2D) carbon allotrope, which has been experimentally synthesized and theoretically predicted to show superconductivity. In this work, we investigate functionalized biphenylene with the adsorption of Li. The superconducting critical temperature (Tc) can be pushed from 0.59 K up to 3.91 K after Li adsorption. Our calculations confirm that the adsorption pushes the peak showing a high electronic density of states closer to the Fermi level, which usually leads to a larger Tc. Furthermore, the application of biaxial tensile strain can soften phonons and further enhance the Tc up to 15.86 K in Li-deposited biphenylene. Interestingly, a pair of type-II Dirac cones below the Fermi level has been observed, expanding the range of Dirac materials. It suggests that monolayer biphenylene deposited with Li may be a material with potential applications and improves the understanding of Dirac-type superconductors.

Theoretical prediction of superconductivity in two-dimensional MXenes of molybdenum carbides.

Theoretically and experimentally, MXenes consisting of Mo and C have aroused much interest due to superconductivity in their films and even monolayer forms. Here, based on first-principles calculations, we systematically calculate the electronic structure, phonon dispersion, and electron-phonon coupling (EPC) of monolayer Mo2C (both T- and H-phases), Mo3C2, and Mo3C3. The results show that H-MoxCy (x = 2 or 3, y = 1-3) always have lower total energies than their corresponding T phase and other configurations. All these two-dimensional (2D) molybdenum carbides are metals and some of them display weak phonon-mediated superconductivity at different superconducting transition temperatures (Tc). The Mo 4d-orbitals play a critical role in their electronic properties and the Mo atomic vibrations play a dominant role in their low-frequency phonons, EPC, and superconductivity. By comparison, we find that increasing the Mo content can enhance the EPC and Tc. Besides, we further explore the impact of strain engineering on their superconducting related physical quantities. With increasing biaxial stretching, the phonon dispersions are gradually softened to form some soft modes, which can trigger some peaks of α2F(ω) in the low-frequency region and evidently increase the EPC λ. The Tc of H-Mo2C can be increased up to 11.79 K. Upon further biaxial stretching, charge density waves may appear in T-Mo2C, H-Mo3C2, and H-Mo3C3.

Influence of cadmium and microplastics on physiological responses, ultrastructure and rhizosphere microbial community of duckweed.

The combined contamination of heavy metals and microplastics is widespread in freshwater environments. However, there are few researches on their combined effects on aquatic plants. In this study, the effects of single and combined stress of 0.01 mg L-1 cadmium (Cd), 50 mg L-1 polyethylene and 50 mg L-1 polypropylene for 15 days on the physiological response, ultrastructure and rhizosphere microbial community of duckweed were investigated. The results showed that Cd and microplastics single or combined stress inhibited the growth of duckweed, shortened the root length and decreased the chlorophyll content. Compared with single Cd treatments, the combination of microplastics and Cd increased duckweed growth rate and increased superoxide dismutase activity and malondialdehyde content and reduced chloroplast structural damage, indicating that the combined stress could reduce the toxicity of heavy metals to duckweed. Through the study of rhizosphere microbial diversity, 1381 Operational Taxonomic Unit (OTUs) were identified and rich microbial communities were detected in the duckweed rhizosphere. Among them, the main microbial communities were Proteobacteria, Bacteroidetes, and Cyanobacteria. Compared with Cd single stress, the ACE and chao index of rhizosphere microbial community increased under combined stress, indicating that the diversity and abundance of microbial communities were improved after combined stress treatment. Our study revealed the effects of heavy metals and microplastics on aquatic plants, providing a theoretical basis for duckweed applications in complex water pollution.

Effects of different doses of magnesium sulfate on pneumoperitoneum-related hemodynamic changes in patients undergoing gastrointestinal laparoscopy: a randomized, double-blind, controlled trial.

BACKGROUND: The infusion of magnesium sulfate is well known to reduce arterial pressure and attenuate hemodynamic response to pneumoperitoneum. This study aimed to investigate whether different doses of magnesium sulfate can effectively attenuate the pneumoperitoneum-related hemodynamic changes and the release of vasopressin in patients undergoing laparoscopic gastrointestinal surgery. METHODS: Sixty-nine patients undergoing laparoscopic partial gastrectomy were randomized into three groups: group L received magnesium sulfate 30 mg/kg loading dose and 15 mg/kg/h continuous maintenance infusion for 1 h; group H received magnesium sulfate 50 mg/kg followed by 30 mg/kg/h for 1 h; and group S (control group) received same volume 0.9% saline infusion, immediately before the induction of pneumoperitoneum. Systemic vascular resistance (SVR), cardiac output (CO), mean arterial pressure (MAP), heart rate (HR), central venous pressure (CVP), serum vasopressin and magnesium concentrations were measured. The extubation time, visual analogue scale were also assessed. The primary outcome is the difference in SVR between different groups. The secondary outcome is the differences of other indicators between groups, such as CO, MAP, HR, CVP, vasopressin and postoperative pain score. RESULTS: Pneumoperitoneum instantly resulted in a significant reduction of cardiac output and an increase in mean arterial pressure, systemic vascular resistance, central venous pressure and heart rate in the control group (P <  0.01). The mean arterial pressure (T2 - T4), systemic vascular resistance (T2 - T3), central venous pressure(T3-T5) and the level of serum vasopressin were significantly lower (P <  0.05) and the cardiac output (T2 - T3) was significantly higher (P <  0.05) in group H than those in the control group. The mean arterial pressure (T4), systemic vascular resistance (T2), and central venous pressure(T3-T4) were significantly lower in group H than those in group L (P <  0.05). Furthermore, the visual analog scales at 5 min and 20 min, the level of vasopressin, and the dose of remifentanil were significantly decreased in group H compared to the control group and group L (P <  0.01). CONCLUSION: Magnesium sulfate could safely and effectively attenuate the pneumoperitoneum-related hemodynamic instability during gastrointestinal laparoscopy and improve postoperative pain at serum magnesium concentrations above 2 mmol/L. TRIAL REGISTRATION: The study was retrospectively registered at Chinese Clinical Trial Registry; the registration number is ChiCTR-IPD-17011145, principal investigator: D.Y. Q., date of registration: April 13, 2017.

Catalytic Enantioselective Cyclopropenation of Internal Alkynes: Access to Difluoromethylated Three-Membered Carbocycles.

Herein we described an efficient RhII -catalyzed enantioselective cyclopropenation reaction of internal alkynes with a masked difluorodiazoethane reagent (PhSO2 CF2 CHN2 , Ps-DFA). This asymmetric transformation offers efficient access to a broad range of enantioenriched difluoromethylated cyclopropenes (40 examples, up to 99 % yield, 97 % ee). The synthetic utility of obtained strained carbocycles is demonstrated by subsequent stereodefined processes, including cross-couplings, hydrogenation, Diels-Alder reaction, and Pauson-Khand reaction.

The role of MNK1-mTORC1 pathway in modulating macrophage responses to Vibrio vulnificus infection.

Vibrio vulnificus (Vv) is known to cause life-threatening infections, particularly septicemia. These patients often exhibit elevated levels of pro-inflammatory cytokines. While it is established that mitogen-activated protein kinase (MAPK)-interacting kinase (MNK) contributes to the production of pro-inflammatory cytokines, the role of MNK in macrophages during Vv infection remains unclear. In this study, we investigate the impact of MNK on macrophages. We demonstrate that the inhibition of MNK in J774A.1 cells, when treated with lipopolysaccharide or Vv, resulted in decreased production of tumor necrosis factor alpha and interleukin-6, without affecting their transcription. Interestingly, treatment with MNK inhibitor CGP57380 led to enhanced phosphorylation of MNK1 but decreased phosphorylation of eIF4E. Moreover, MNK1 knockout cells exhibited an increased capacity for phagocytosis and clearance of Vv, with more acidic phagosomes than the parental cells. Notably, CGP57380 did not impact phagocytosis, bacterial clearance, or phagosome acidification in Vv-infected J774A.1 cells. Considering the reported association between MNK and mammalian target of rapamycin complex 1 (mTORC1) activation, we investigated the mTORC1 signaling in MNK1 knockout cells infected with Vv. Our results revealed that attenuation of the mTORC1 signaling in these cells and treatment with the mTORC1 inhibitor rapamycin significantly enhanced bacterial clearance in J774A.1 cells following Vv infection. In summary, our findings suggest that MNK promotes the Vv-induced cytokine production in J774A.1 cells without affecting their transcription levels. MNK1 appears to impair the phagocytosis, bacterial clearance, and phagosome acidification in Vv-infected J774A.1 cells through the MNK1-mTORC1 signaling pathway rather than the MNK1-eIF4E signaling pathway. Our findings highlight the importance of the MNK1-mTORC1 pathway in modulating macrophage responses to Vv infection. IMPORTANCE: Mitogen-activated protein kinase (MAPK)-interacting kinase (MNK) plays a role in promoting the production of tumor necrosis factor alpha and interleukin-6 in macrophages during Vibrio vulnificus (Vv) infection. Inhibition or knockout of MNK1 in J774A.1 cells resulted in reduced cytokine production without affecting their transcription levels. MNK1 also impairs phagocytosis, bacterial clearance, and phagosome acidification in Vv-infected cells through the MNK1-mammalian target of rapamycin complex 1 (mTORC1) signaling pathway. The findings highlight the importance of the MNK1-mTORC1 pathway in modulating macrophage responses to Vv infection.

Enantioselective sulfur(VI) fluoride exchange reaction of iminosulfur oxydifluorides.

Linkage chemistry and functional molecules derived from the stereogenic sulfur(VI) centre have important applications in organic synthesis, bioconjugation, drug discovery, agrochemicals and polymeric materials. However, existing approaches for the preparation of optically active S(VI)-centred compounds heavily rely on synthetic chiral S(IV) pools, and the reported linkers of S(VI) lack stereocontrol. A modular assembly method, involving sequential ligand exchange at the S(VI) centre with precise control of enantioselectivity, is appealing but remains elusive. Here we report an asymmetric three-dimensional sulfur(VI) fluoride exchange (3D-SuFEx) reaction based on thionyl tetrafluoride gas (SOF4). A key step involves the chiral ligand-induced enantioselective defluorinative substitution of iminosulfur oxydifluorides using organolithium reagents. The resulting optically active sulfonimidoyl fluorides allow for further stereospecific fluoride-exchange by various nucleophiles, thereby establishing a modular platform for the asymmetric SuFEx ligation and the divergent synthesis of optically active S(VI) functional molecules.

Subcellular distribution, chemical forms of cadmium and rhizosphere microbial community in the process of cadmium hyperaccumulation in duckweed.

Duckweed is a newly reported Cd hyperaccumulator that grow rapidly; however, little is known about its tolerance and detoxification mechanisms. In this study, we investigated the tissue, subcellular, and chemical form distribution of the Cd in duckweed and studied the influences of Cd on duckweed growth, ultrastructure, and rhizosphere microbial community. The results showed that Cd could negatively affect the growth of duckweed and shorten the root length. More Cd accumulated in the roots than in the leaves, and Cd was transferred from the roots to the leaves with time. During 12-24 h, Cd mainly existed in the cell wall fraction (2.05 %-95.52 %) and the organelle fraction (5.03 %-97.80 %), followed the soluble fraction (0.14 %-16.98 %). Over time, the proportion of Cd in the organelles increased (46.64 %-92.83 %), exceeding that in the cell wall (6.79 %-66.23 %), which indicated that duckweed detoxification mechanism may be related to the retention of cell wall and vacuole. The main chemical form of Cd was the NaCl-extracted state (30.15 %-88.66 %), which was integrated with pectate and protein. With increasing stress concentration and time, the proportion of the HCl-extracted state and HAc-extracted state increased, and they were low-toxic Cd oxalate and Cd phosphate, respectively. Cd damaged the ultrastructure of cells such as chloroplasts and mitochondria and inhibited the diversity of microbial communities in the duckweed rhizosphere; however, the dominant populations that could tolerate heavy metals increased. It was speculated that duckweed distributed Cd in a less toxic chemical form in a less active location, mainly through retention in the root cell wall and sequestration in the leaf vacuoles, and is dynamically adjusted. The rhizosphere microbial communities tolerate heavy metals may also be one of the mechanisms by which duckweed can tolerate Cd. This study revealed the mechanism of duckweed tolerance and detoxification of Cd at the molecular level and provides a theoretical basis for further development of duckweed.

Physiological response, microbial diversity characterization, and endophytic bacteria isolation of duckweed under cadmium stress.

Duckweed is a cadmium (Cd) hyperaccumulator. However, its enrichment characteristics and physiological responses to Cd have not been systematically studied. The physiological responses, enrichment characteristics, diversity of endophytic bacterial communities, and isolation of Cd-resistant endophytes in duckweed (Lemna minor 0014) were studied for different durations and Cd concentrations. The results indicated that peroxidase (POD) and catalase (CAT) activities decreased while superoxide dismutase activity first increased and then decreased with increasing Cd stress duration. POD activities, CAT activities, and O2- increased as Cd concentrations increased. Malondialdehyde content and Cd accumulation in duckweed increased with increasing concentrations and time. This endophytic diversity study identified 488 operational taxonomic units, with the dominant groups being Proteobacteria, Firmicutes, and Actinobacteria. Paenibacillus sp. Y11, a strain tolerant to high concentrations of Cd and capable of significantly promoting duckweed growth, was isolated from the plant. Our study revealed the effects of heavy metals on aquatic plants, providing a theoretical basis for the application of duckweed in water pollution.